{
  "bibcode": "2009GCN..9874....1O",
  "body": "F. Olivares, P. Afonso, J. Greiner (all MPE Garching), S. McBreen (MPE + \nUCD), T. Kruehler, A. Rau, A. Yoldas, G. Kanbach (all MPE), and S. Klose \n(TLS Tautenburg) report on behalf of the GROND team:\n\nThe field of GRB 090902B, (Fermi GBM trigger 273582310/090902462, Bissaldi \net al., GCN #9866) which was detected by the LAT (de Palma et al., GCN \n#9867), was observed simultaneously in g'r'i'z'JHK with GROND (Greiner et \nal. 2008, PASP 120, 405) mounted at the 2.2 m ESO/MPI telescope at LaSilla \nObservatory (Chile).\n\nObservations started at 00:21 UT on September 3, 2009, 13.25 hours after \nthe GRB trigger. They were performed at a seeing of around 2\", at an \naverage air mass larger than 2.0 and under variable sky conditions. We \ndetect a NIR source within the Swift/XRT error circle reported by Kennea et \nal. (GCN #9868) and on the edge of the Swift/XRT enhanced position (Evans \net al. GCN #9871), at:\n\nRA (J2000.0) = 17h 39m 45.41s\nDEC (J2000.0) = +27d 19' 27.1\"\n\nwith an uncertainty of 0.5\" in each coordinate.\n\nThis position seems consistent with the object reported by Perley et al. \n(GCN #9870) and is very likely the source reported by Swenson & Siegel (GCN \n#9869).\n\nThe source is not in the field of view of the griz channels, so no \nstatement can be made about the optical bands.\n\nThe afterglow (Cucchiara et al. GCN #9873) has the following preliminary AB \nmagnitude and shows tentative evidence of fading within the observations.\n\nmidtime         J_AB mag\n  -----------------------------------------------\n01:09:31 UT     20.26 +/- 0.07\n\nCalibrations was done against 2MASS catalog stars. No Galactic extinction \ncorrection was applied.",
  "circularId": 9874,
  "createdOn": 1251969290000,
  "email": "kruehler@mpe.mpg.de",
  "subject": "GRB 090902B: GROND NIR Afterglow Observations",
  "submitter": "Thomas Kruehler at MPE/MPI  <kruehler@mpe.mpg.de>",
  "eventId": "GRB 090902B"
}